This paper concentrates on controversies about children's consent, and reviews how children's changing status as competent decision makers about healthcare and research has gradually gained greater respect. Criteria for competence have moved from age towards individual children's experience and understanding. Uncertain and shifting concepts of competence and its identification with adulthood and childhood are examined, together with levels of decision-making and models for assessing children's competence. Risks and uncertainties, methods of calculating the frequency and severity of risks, the concept of 'therapeutic research' and problems of expanding consent beyond its remit are considered. The paper ends by considering how strengths and limitations in children's status and capacities to consent can be mirrored in researchers' and practitioners' own status and capacities. Examples are drawn from empirical research studies about decision-making in healthcare and research involving children in the UK.